The natural explanation of this is that all three wrote in the apostolic age, and consequently had access, each of them independently of the other two, to the most authentic sources of information. These sources (so far as the evangelists were not themselves eye-witnesses) lay partly, perhaps, in written documents like those referred to by Luke, 1:1, partly in the unwritten traditions current in the apostolic churches, and partly in personal inquiry from eye-witnesses, especially, in the case of Mark and Luke, from apostles themselves. From these materials each selected as suited his purposes, and the churches everywhere unhesitatingly received each of the three gospels, notwithstanding the above-named variations between them, because they had undoubted evidence of their apostolic authority. We cannot suppose that after the apostolic age three gospels, bearing to each other the relation which these do, could have been imposed upon the churches as all of them equally authentic. We know from the history of Marcion's gospel how fully alive they were to the character of their sacred records. On apostolic authority they could receive—to mention a single example—both Matthew's and Luke's account of our Lord's genealogy; but it is certain that they would not have received the two on the authority of men who lived after the apostolic age.
16. In the gospel narratives are numerous incidental allusions to passing events without the proper sphere of our Lord's labors, to social customs, and to the present posture of public affairs, civil and ecclesiastical. In all these the severest scrutiny has been able to detect no trace of a later age. This is a weighty testimony to the apostolic origin of the gospels. Had their authors lived in a later age, the fact must have manifested itself in some of these references. The most artless writer can allude in a natural and truthful way to present events, usages, and circumstances; but it transcends the power of the most skilful author to multiply incidental and minute references to a past age without betraying the fact that he does not belong to it.
17. Every age has, also, its peculiar impress of thought and reasoning in religious, not less than in secular matters. Although the gospel itself remains always the same, and those who sincerely embrace it have also substantially the same character from age to age, there is, nevertheless, continual progress and change in men's apprehension of the gospel and its institutions, and consequently in their manner of reasoning concerning them. No man, for example, could write a treatise on Christianity at the present day without making it manifest that he did not belong to the first quarter of the present century. The primitive age of Christianity is no exception to this universal law. Under the auspices of the apostles it began to move forward, and it continued to move after their decease. The pastoral epistles of Paul bear internal marks of having been written in the later period of his life, because they are adapted to the state of the Christian church and its institutions that belonged to that, and not to an earlier period. If, now, we examine the writings of the so-called apostolic fathers—disciples of the apostles, who wrote after their death—we find in them circles of thought and reasoning not belonging to the canonical writings of the New Testament, least of all to the canonical gospels, though they are evidently derived from hints contained in these writings, whether rightly or wrongly apprehended. In this respect, the works of the apostolic fathers are distinguished in a very marked way from those which bear the names of the apostles themselves or their associates.
18. Another decisive argument lies in the character of the Greek employed by the evangelists, in common with the other writers of the New Testament. It is the Greek language employed by Jews, (or, in the case of Luke, if his Jewish origin be doubted—see Col. 4:11, 16—by one who had received a Jewish training under the influence of the Greek version of the Old Testament,) and therefore pervaded and colored by Hebrew idioms. This peculiar form of the Greek language belongs to the apostolic age, when the teachers and writers of the church were Jews. After the overthrow of Jerusalem, the dispersion of the Jewish nation, and the death of the apostles and their associates, it rapidly disappeared. Thenceforward the writers of the church were of Gentile origin and training, in accordance with the Saviour's memorable words: "The kingdom of God shall be taken from you, and given to a nation bringing forth the fruits thereof."
These internal proofs, coinciding as they do with a mass of external evidences so great and varied, place the genuineness of the four canonical gospels on a foundation that cannot be shaken.